[Stoves] air pumps, stoves and unintended effects

[drew]

    The use of forced air in combustion has been historically associated 
with metal foundry's and blacksmiths for the last few thousand years.    
To attain high heat and reasonable efficiency these ancient craftsmen 
regularly used forced air to forge and melt various metals (including 
iron) and occasionally glass.   The air pumping systems they used varied 
from their own lungs to feather pistons in bamboo tubes.   One common 
thing that I have noticed is that they often would use a low volume/high 
pressure air pump (the high pressure I am referring to is relative).   
This pump would be used to create a high speed jet of air that would be 
directed through an inductor to create the higher volume lower pressure 
desired.    The pumps would often occur in pairs with both jets aimed 
into the inductor, this eliminates the need for flapper valves.    These 
people were able to make their own equipment from local materials.

As I understand it the goals of the stoves program are

   1. reduce the occurrence of health complaints caused by indoor
      pollution from cooking and heating stoves
   2. increase the efficiency of the stoves and heaters to reduce the
      demand for wood and charcoal
   3. create or support local industry and encourage a feeling of self
      reliance
   4. potentially to introduce a small source of electricity (via
      thermocouple or ?)

The use of electric fans, pulse width modulation controllers,  and 
thermocouples certainly meets some of those goals, but I wonder what the 
unintended  effect would be.    I fear that if a thermocouple system 
like the Phillips system were made able to supply enough energy to 
provide some lighting, that it could become a primary use of the stove, 
increasing the demand for wood, and greatly increasing the frequency of 
it's use.    To give the problem of energy required to electrically 
solve the air pumping problem vs. human pumping some scale consider:   A 
human athlete is generally considered to be able to provide 350w /hour 
for a few hours.   This is considered the upper end of human output.    
The fans talked about here seem to be in the 5w range and it seems most 
people think that they may need to be regulated to a lower output than 
that.     As someone who black smithed professionally for 10 years 
(mostly using propane for convince) I spent many hours pumping bellows, 
and it was very little work, considering the enormous btu outputs, and 
fuel consumptions (we would consume around 50-75lbs of good coal per day 
per heath, with one or two smiths per hearth).    I was fortunate to 
occasionally work at historic sites as a demonstrator and there often 
found bellows that had a reservoir bellow, allowing the air blast to 
continue uninterrupted for quite some time with out my pumping.   

An interesting side issue re:coal and steam was that we always used 
soaking wet coal, and watered our fires all the time.   This is what I 
was trained to do.   I was told that the steam conducted the heat, and 
chemically helped the coal to crack into coke.    I have sometimes 
worked at forges where people weren't familiar with watering coal, and 
have found that once they tried it, they were hooked finding their fire 
much hotter, and easier to manage.

While I think that using forced air is a good and historically supported 
solution to efficient combustion, and I can understand our first world 
attraction to the convince of fans and electricity I would encourage 
people who are exploring these types of solutions to look at man powered 
air pumps of which there are a myriad of historical examples.   People 
might also consider using a manometer on their combustion chambers to 
help make the systems modular.    Someone might come up with a great air 
pumping solution but an less than perfect stove.  Having some idea of 
what needs and outputs are for different design stoves and pumps, 
electric or otherwise would help to make the systems more modular.
   
    Unintended consequences can be more dangerous than the original 
problem but hopefully with foresight can be avoided or mitigated.    I 
don't know where I heard it but I read that stoves programs have already 
had an unintended consequence in the roofs of some homes.   Apparently 
the toxic smoke that was regularly produced by the traditional fires 
would serve as a fungicide and insecticide, extending the lifetime of 
some thatched roofs.  I think that most people are happy with thier 
improved health, and the reduced need for fuel but I think the 
unintended consequences of changes encouraged from the first world 
should be carefuly examined before they are promoted wholesale.

-- 
This message is intended only for the addressee(s)and may contain information that is confidential and/or copyright.  If you are not the intended recipient please notify me by reply email and immediately delete this email. Use, disclosure or reproduction of this email by anyone other than the intended recipient(s) is strictly prohibited.